The present invention relates to a extensible elastic tab useable as a fastening tab for closure of limited use garments and disposable absorbent articles such as diapers and incontinent briefs, training pants, diaper liners, sanitary hygiene articles and the like.
The provision of elastic on or adjacent the body engaging portions of limited use garments and disposable absorbent garments is widespread both in the patent art and in commercial products, where generally elastic films, strands, nonwovens or foam materials are used. These elastic materials when applied directly to a limited use garment or disposable absorbent article, in the area intended to engage a body portion of a wearer, are generally applied to the garment or article in an extended state. When the extended elastic recovers it gathers the material forming the body engaging portion, of the disposable absorbent article or limited use garment or the like, to which the elastic is attached. It has been proposed to provide only sections of the body-engaging portion with elastic. For example, in U.S. Pat. Nos. 4,857,067; 5,156,973 and 4,381,781, it has been proposed that elastic be provided only in an outwardly extending ear portion of a diaper. By placing the elastic in this outwardly extending ear portion, the engaging effect of the elastic is not deadened by reinforcement with the absorbent core. For example, when elastic in placed on a waistband portion (where elastic is typically located), the elastic can be reinforced by the absorbent core structure below the waistband. In U.S. Pat. No. 4,857,067 the elastic used is preferably a heat-shrinkable elastic which is applied in an extended unstable condition and allowed to recover by the application of heat. This causes the inelastic material of the ear portion attached to the elastic to gather. In U.S. Pat. No. 5,156,743 the elastic material is a conventional film-like elastic which is applied to a diaper in the ear portion in an untensioned state followed by a localized stretching of the resulting laminate in a location where the elastic is attached by meshing corrugating rolls which intermittently engage and disengage with the laminate material in a machine direction. The inelastic material of the ear is permanently deformed by this localized stretching and the deformed inelastic material gathers when the attached stretched elastic recovers. In U.S. Pat. No. 4,381,781 an elastic film is located in an ear portion of a diaper where non-elastic material in the ear portion has been cut out or removed so the elastic can be applied in an untensioned state and be relatively unhindered when extended.
It has also been proposed to provide elastic material outside the side edge of a disposable absorbent garment or the like in association with a fastening element. The fastening element when grasped, tensioned and secured causes the elastic to extend. The extended elastic then tensions the body-engaging portion to which it is operably attached. This approach is desirable in that the elastic need not be attached to the inelastic elements of the article in an extended state, which is difficult and the elastic is not reinforced by attached or adjacent inelastic material forming the article and its components. For example, providing a fastening tape or tab having a specific elastic region, is disclosed in U.S. Pat. No. 5,057,097 which proposes forming a fastening tab where the tab backing is a multi-layer film formed of an elastic center layer and inelastic outer layers. The coextruded material described must be stretched beyond a yield point or range after which the coextruded material exhibits elastic properties in a central region. Generally, the coextruded materials described were elongated to approximately 400%. Generally the force at 50% elongation for the second pull of the elastic material is a fraction of this 50% force of the inelastic material for the initial elongation. This is not desirable for a material that may be used on the first pull. Furthermore, the performance of this material is unpredictable in use. The end user has no clear indication of where they must stop pulling the elastic material in order to achieve activation (e.g., the initial force at 50% elongation is substantially the same as the initial force at 400% elongation). This initial elongation is important as the elastic performance in use, (i.e. on the second and subsequent pulls) is dictated by the extent to which the materials is initially stretched. The user may choose to extend the material 50% or 700% or somewhere in between. As such, the elastic performance in use is extremely variable depending on the particular user and how far he or she chooses to extend the tab initially.
Another elasticated fastening tape product is disclosed in European Patent 704196, which indicates that conventional elastic fastening tapes are provided by laminating the ends of stretchable and unstretchable portions, which provide unreliable connections in industrial conditions. This patent proposed that the entire stretchable elastic material be continuously attached to a center portion of a fastening tab which center portion is then subsequently selectively stretched by passing that portion of the laminate material through meshed corrugating rolls. This solution of course results in some of the same problems as attaching the elastic to the garment itself.
U.S. Pat. No. 5,549,592 describes a laminated fastening tape tab where the same problem of a weak bond between the ends of an elastic panel and a fastening tab is addressed by providing a reinforcement strip at this bonding location.
The provision of elastic panels on the outside of a disposable absorbent garment is also discussed in U.S. Pat. No. 5,669,897 (2 elastic panels are provided with different directions of extensibility attached at one end to a fastening tab and at the other end to the side edge of the disposable absorbent garment). U.K. Patent Application 2,284,742, which is similar to U.S. Pat. No. 5,549,592, provides a specific reinforcement material at the location near a fastening tab is joined to an elastic panel section. However, this reinforcement is provided at locations other than directly at the bond point between the fastening tab and the elastic panel providing a xe2x80x9cstress beam sectionxe2x80x9d to facilitate in the distribution of forces across the elastic panel. U.S. Pat. No. 5,399,219 also discloses an elastic panel fastening tab similar to that of U.S. Pat. No. 5,549,592, however providing a stiffening material which is attached to both the tape backing material and the side panels. In U.S. Pat. Nos. 5,593,401; 5,540,796 and U.K. Application 2,291,783 side panels are attached to bridging members which connect to laterally opposed side panels.
The invention relates to an extensible elastic tab designed to be adhered to the edge of an article, formed using a coextruded elastic film comprising at least one elastic layer and at least one second layer on at least a first face of the elastic layer. One face of the coextruded elastic film is attached to at least a partially extensible nonwoven layer. The partially expandable, or extensible nonwoven layer has at least one first portion with limited extensibility in a first direction and at least one second inextensible portion in the first direction. The extensible elastic tab when stretched to the extension limit of the first portion or portions in the first direction will elastically recover at least 1.0 cm, preferably at least 2 cm providing an elastic tab having a Useful Stretch Ratio (as defined in the Examples) of at least 30 percent. The Useful Stretch Ratio includes the portion of the elastic recovery length having an elastic recovery force of greater than 20 grams/cm force, but below a given extension which generally is 90 percent of the extension limit. Further the elastic tab in the region of the Useful Stretch Ratio preferably has an incremental extension force of less than about 300 grams/cm. The coextruded elastic film second layer is preferably a relatively inelastic material or blend and provided on both faces of the at least one elastic layer.